1. Field Of The Invention
This invention is related to a personal dosimeter for registering gaseous contaminants in the atmosphere. More particularly, it is related to an integrating dosimeter useful in measuring the average exposure level to a gaseous contaminant over a given period of time.
1. Description Of The Prior Art
Monitoring of pollutants in the air is increasingly important as the harmful effects of such pollutants become evident. In large work-places, for example, one device for this purpose has used a pump which forces the air to be sampled in a continuous, uniform stream over a sensing element. Such devices do not, however, accurately monitor the exposure of a moving individual within the large area being sampled.
Personal sampling devices which are worn by individual workers and which passively collect the contaminants have also been used. Devices which employ the molecular diffusion of the monitored gaseous contaminant to collect the sample have been shown, for example, in U.S. Pat. Nos. 3,924,219 and 3,985,017. Many devices which allow the gaseous contaminant to diffuse to a collecting medium can give inaccurate indications of average contaminant concentration because the devices collect varying amounts of contaminant, being adversely affected by atmospheric circulation patterns or motion of the individual wearing the device.
The solution to this problem employed in prior art devices, which has essentially involved restricting the diffusion rate, has often made the device somewhat insensitive to low concentrations of the gaseous contaminants. Therefore, there remains a need for a dosimeter which is independent of relative atmospheric motion and which operates satisfactorily at low contaminant concentrations.